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Un ITED sTATEs PATENT oEEroE.

JOHN T. PLASS, OF NEV YORK, N. Y.

SLIDE-VALVE FOR STEAM-ENGINES.

Specification of Letters Patent No. 2?,381, dated March 6, 1860.

To all whom it may concern.'

Be it known that I, JOHN T. PLAss, of the city, county, and State of New York, have invented a new and useful Improvement for Relieving the Slide-Valves of Steam-Engines of Unnecessary Pressure; and I hereby declare that the following is a full, clear, and exact description of the same, reference being had to the accompanying drawings, forming part of this specification, in which Figure l is a longitudinal section of a slide valve and steam chest illustrating the application of my invention. Fig. 2 is a top view of the steam chest.

Similar letters of reference indicate corresponding parts in the two figures.

To enable others skilled in the art to apply my invention I will proceed to describe its construction and operation.

A, is the steam chest, and a, a, is the valve seat.

B, is the slide valve having its back planed and ground perfectly flat and smooth, and parallel with its face.

C, is the follower, against which the back of the valve works, made of the form of an inverted cylindrical cup, fitted to a stufling box D, in the back of the steam chest, and prescribing an external area nearly equal to that of the whole face of the valve, or equal to so much of the said face as it is desired to relieve of the pressure of steam acting to force it toward the seat.

e, e, is the packing of the stuffing box D.

E, is the gland of the stuiing box held in its place by screws c, o, screwing into the sides of the stuffing box. This gland is made with a head (Z, in the center of which is fitted the set screw F, by which the follower is held against the plane surface of the back of the valve.

G, is the spring through which the set screw acts upon the follower, made of vulcanized india-rubber, and fitted into a small cup f, f, provided in the head of the followergand g, is a small plate of metal, fitted to the cup f, f, above or outside of the spring to form a bearing for the end of the set screw F, and preventin the latter indenting itself into and destroying the spring. The spring may however be of steel and applied in any convenient manner between the set screw and the head of the follower.

The form and extent of area of the back of the valve should be such that, in the working of the valve, the face of the follower will never be exposed to the steam in the chest, and for this purpose flanges b, are provided around it to give the required form and extent of area.

t, t, are the openings in the head of the follower for the escape of any steam that may leak between the back of the valve and the face of the follower; and z', z', are openings provided in the head of the gland for the escape of such leakage of steam to the atmosphere for the detection of the leakage.

To put the valve in working condition the follower is adjusted to its back by screwing down the set screw to such a degree as to produce just pressure enough to hold the valve to its seat and prevent the escape of steam between its back and the follower. The valve then works with perfect freedom and with very little friction, the spring allowing the follower to yield to the expansion of the metal of the valve and follower and so preventing any great friction being produced by such expansion, or by the screw being accidentally screwed down too tightly, and yet serving to keep the follower in contact with the back of the valve, and the valve to its seat, and compensating for wear between the valve and the seat and follower. Then any leakage-of steam through the openings z', z', is observed, the set screw wants screwing down, or, if that is not sufficient to prevent it, the surfaces of the back of the valve and face of the follower require re-grinding.

It is obvious that the follower, set screw and spring may be applied in a similar manner when a separate slide valve is employed for each end of the cylinder as well as the single valve represented, a separate follower, stufling box, set-screw, and spring being of course required for each valve.

I do not claim broadly the employment of a spring and adjusting screw upon the backs of slide valves, but:

What l claim as my invention, and desire to secure by Letters Patent, is

l. rlhe arrangement in connection with the follower C, of the cup f, spring G, gland E, and exterior adjusting screw F, as and for the purpose herein shown and described.

2. The combination of the stufng box D,

With the follower C, and gland E, as and thus notify the attendant of the leakage and for the purpose herein shown and described. enable him to regulate the adjustment of the 3. The combination of the openings (h,) valve accordingly.

(la) in the follower C, With the openings JOHN T. PLASS. 5 (i, z',) in the gland E, as shown7 so that any Witnesses:

steam which escapes under the force of the S. H. WALES,

Valve Will find exit to the atmosphere and C. M. HUGHES. 

